Pipe jacking is often referred to as a guided, trenchless method for installation of pipe sections under obstacles. A tunnel is formed using a drilling head, which is pushed further and further into the ground by reinforced concrete jacking pipes pushed behind it, in series. The pushing (or “jacking”) is performed using several sets of hydraulic jacks. The drilling head usually houses a mechanical digging arm or a rotating head, and is steered using hydraulic steering jacks. The drilling head may be remotely controlled and navigated by a human operator and/or in an automatic manner. One way of navigating the drilling head is by emitting a laser beam into the jacked pipes, thereby creating a virtual straight path for the drilling head to follow. However, it is quite common to have curved tunnels formed by pipe jacking, in which case the navigation may intentionally but accurately deviate from the straight path of the laser beam.
As the drilling head excavates soil from its frontal area, the soil may be evacuated backwards using one or more conveyors or a pipeline with one or more pumps. Some drilling heads are also equipped for grinding the excavated soil, for easier evacuation. It is also customary to fluidize the soil using one or more suitable agents, to make its evacuation even easier.
Pipe jacked tunnels are commonly manufactured with diameters ranging from 120 cm to 400 cm, however smaller and larger tunnels do exist occasionally. In ground conditions where the tunnel can be exposed to additional pressures due to the plasticity of the ground, intermediate jacking stations are sometimes introduced, to reduce the pressures. The intermediate jacking stations provide for sections of the pipeline (namely, sections formed of multiple jacking pipes) to be independently moved, which reduces the force which the hydraulic jacks, at the entrance to the tunnel, have to apply. In cases of high plasticity ground conditions, reducing of the pressure is also often achieved by lubricating the outer annulus of the pipelines.
A jacking pipe may be made in a way that allows a serial connection of multiple jacking pipes, which finally form the desired tunnel. While the tunnel is being formed, a set of metal pipes is introduced into the serially-connected jacking pipes, to form a conduit in which a fluid will flow. The metal pipes are then welded to one another while introduced process. The welding makes the set of metal pipes form an elongated, sealed conduit within the jacking pipes and along the tunnel.
The foregoing examples of the related art and limitations related therewith are intended to be illustrative and not exclusive. Other limitations of the related art will become apparent to those of skill in the art upon a reading of the specification and a study of the figures.